Comparative Evaluation of Marshall Properties for Crumb Rubber Modified AC-BC and AC-WC Asphalt Mixtures using the Dry Process

Abstract

This study evaluates the mechanical and volumetric performance of asphalt mixtures modified with crumb rubber (CR) using the dry process. Road infrastructure demands high-quality materials to ensure durability and accommodate increasing traffic loads. The research compares two types of mixtures: Asphalt Concrete-Wearing Course (AC-WC) and Asphalt Concrete-Binder Course (AC-BC). Five different asphalt contents (5%, 5.5%, 6%, 6.5%, and 7%) were tested, with the addition of 3% and 5% crumb rubber by weight of the fine aggregate. Performance was assessed based on Marshall Test parameters, including stability, flow, and volumetric properties such as Voids Filled with Asphalt (VFA) and Voids in the Mixture (VIM). Results indicated that while the addition of crumb rubber generally increased VFA and inversely decreased VIM, it had a counterproductive effect on Marshall stability in certain concentrations. The study concludes that the AC-BC mixture with 3% crumb rubber provides the most balanced performance in terms of strength and durability compared to higher rubber contents. These findings suggest that 3% CR modification in binder courses offers a viable alternative for improving road pavement quality.